A cell component of blood is roughly classified into platelet, leukocyte and erythrocyte and, further, leukocyte is classified into granulocyte (eosinophil, neurtrophil, and basophil), monocyte and lymphocyte. These cells are produced in bone marrow, are differentiated and matured from an immature cell, and migrated to peripheral blood. In the case of a healthy person, immature leukocyte which has not been matured to leukocyte contained in normal blood, such as granulocyte, monocyte and lymphocyte (hereinafter, these are referred to as “mature leukocyte” in some cases) does not appear in peripheral blood, but in peripheral blood of a patient with leukemia, cancer bone marrow metastasis or serious infectious disease, immature leukocyte such as myeloblast appears in some cases. Particularly, detection of myeloblast is important for diagnosing the aforementioned diseases.
As a method for automatically measuring blood collected in a clinical test or a medical examination, a measuring method utilizing flowcytometry is utilized. Flowcytometry is a method of introducing a sample obtained by fluorescently staining a cell membrane or a nucleus into a flow cell, irradiating a cell passing through a flow cell with excitation light of a dye, obtaining information regarding scattered light or fluorescent light emitted from individual cells passing through a flow cell, and measuring a kind and the number of cells from the information.
In a method for measuring a hematological sample using flowcytometry, various methods for detecting a hemocyte contained in blood, and further, immature leukocyte appearing in the case of a hemocyte disease, and a hemocyte whose form has been changed by discriminating them from other hemocyte cells are proposed.
For example, according to the technique of US2005/0202400, a hemocyte in blood is classified as in the following (1) to (3). (1) First, in a two-dimensional scattergram using a forward scattered light peak and a forward scattered light width as two axes, platelet aggregation, and leukocyte and an erythrocyte ghost are discriminated. (2) Next, leukocyte and erythrocyte ghosts discriminated in (1) are developed into a two-dimensional scattergram using a forward scattered light intensity and a fluorescent intensity as two axes, and leukocyte, and an erythrocyte ghost are discriminated. (3) Further, leukocyte discriminated in (2) is developed into a two-dimensional scattergram using a fluorescent intensity and a side scattered light intensity as two axes, and leukocyte is sub-classified into lymphocyte, monocyte, granulocyte, myeloblast, and granulocyte immature-cytes.
However, according to US2005/0202400, in (3), myeloblast can be classified, but when a sample containing a small amount of platelet aggregation is measured, there is a possibility that platelet aggregation appears in a region of leukocyte and an erythrocyte ghost in (1), and appears in a region of myeloblast in (3). For this reason, development of the technique for measuring myeloblast at a better precision is desired.